1. Field of the Invention
The present invention relates to a device for converting a video format in a digital television receiver.
2. Background of the Related Art
The digital TV receiver should be capable of processing, and providing videos of different formats, to require a device for converting an input video format into an output video format. As shown in FIG. 1, a related art device for converting a video format is provided with a vertical interpolation unit 11 having a plurality of vertical N:M interpolators 11a, 11b, 11c, —, connected in parallel, a horizontal interpolation unit 12 having a plurality of horizontal N:M interpolators 12a, 12b, 12c, 12d, - - - , connected in parallel, and a multiplexer 13. For example, if a received video format is “720×1280”, the vertical 2:3 interpolator 11a and the horizontal 2:3 interpolator 12a subject the received video format to interpolation, to provide a converted video format of “1080×1920” through the multiplexer 13. And, if the received video format is “480×720”, the vertical 2:3 interpolator 11b and the horizontal 3:8 interpolator 12b subject the received video format to interpolation, to provide a converted video format of “1080×1920” through the multiplexer 13. In other word, the related art device requires many vertical N:M interpolators and many horizontal N:M interpolators depending on a number of received video formats. Thus, since the related art device requires new interpolators every time a new input format is added, the related art device has a disadvantage of having a large size And, the related art device has a disadvantage that a modification of a circuit for adoptation of the new input or output video is not easy. In order to overcome the foregoing disadvantage, as shown in FIG. 2, U.S. Pat. No. 5,528,301 teaches use of 3 filters 21. That is, a decimation filter in FIG. 2 decimates a received video format at a coefficient for each aspect ratio of received video formal. Then, a band limiting filter 22 limits a frequency band, and, finally, an interpolation filter 23 filters the limited video signal, to provide a low frequency band only and to provide a desired video format. However, the use of three filters is costly and results in a large circuit. And, because the determination of filter tap coefficients is complicated, the design is not easy.